Receptors are proteins disposed on the surface of cells. Serotonin, or 5-hydroxytryptamine, receptors are stimulated by serotonin (5-HT) and have been extensively studied. At least seven such 5-HT receptor types are known, denominated 5-HT.sub.1, 5-HT.sub.2, . . . 5-HT.sub.7. 5-HT binds to different ones of these receptors in different ways, to give a signature profile.
The 5-HT receptor types can be further subdivided into subtypes; for example, receptor 5-HT.sub.1 has at least five subtypes denoted A, B, C, D and E. Within an individual subtype there may be further subdivisions. Thus 5-HT.sub.1D subdivides to 5-HT.sub.1D.alpha. and 5-HT.sub.1D.beta..
It is desirable to find pharmaceutical compounds having a high degree of selectivity to a single receptor so that the drug thereof will exhibit reduced side effects.
Given the physiological and clinical significance of the 5-HT.sub.1D receptor, it would be desirable to provide compounds capable of binding tightly and selectively to this receptor. Such compounds have potential medical use, for example, to treat migraine and other disorders for which administration of 5-HT.sub.1D ligand is indicated.